Recently, a technique for writing tracks on a magnetic disk in the high density has been developed. This technique is, e.g., a shingled write recording technique of writing tracks with being partially overlapped with each other. By using this shingled write recording technique, it is possible to write tracks in the high density (write data in tracks in the high density).
It is required to not only write tracks in the high density, but also accurately write tracks. By accurately writing tracks, it is possible to prevent the destruction of data already written on tracks.
Since tracks are written by a write head, however, it is necessary to reduce positioning errors of the write head in order to accurately write tracks. Unfortunately, positioning errors of the write head are affected by a disturbance or the like, and this makes positioning errors of the write head difficult to reduce.
Also, if a track is written in a position shifted from a desired position, the shifted written track must be rewritten. This rewrite may destroy already written tracks or decrease the write speed.